Heretofore, as toothbrushes with enhanced effects of removing dental plaque and cleaning the teeth of narrow portions such as the gaps between neighboring teeth and gaps between the teeth and the gums, a large number of toothbrushes have been proposed with the bristle free end processed into a tapered shape to increase the suitability for bristle insertion into narrow portions. For example, there proposed are various kinds of toothbrushes that have tapered bristles with the bristle free ends tapered, such as a toothbrush which has a tapered shape in which a brush diameter at each portion of a predetermined length from the tapered portion free end portion of the synthetic monofilament achieves a predetermined ratio with respect to the brush diameter at the base in the toothbrush formed by bending synthetic monofilaments with tapered portions on both ends from the center portion and bundling and implanting them in tuft holes as a brush (see Patent Document 1), a toothbrush formed by bending filament bristle tufts in a U-shape and implanted in tuft holes of the brush head by anchor has the shapes of both free ends of the filament varied with one end of the filament formed in a sphere and the other end in a tapered shape, and furthermore, a toothbrush with one end of the filament implanted protrudably from the other free end (see Patent Document 2), a toothbrush that has long tapered bristles and short tapered bristles implanted by tufts (bundles of bristles) in a bristle base and mixed mutually (see Patent Document 3), etc. Furthermore, there proposed are a toothbrush formed by immersing the free end portion of composite synthetic resin filament having a cross-sectional shape with polyamide resin island portions scattered in a polyester resin sea in an acid or alkali solution and dissolving the sea portion to expose the island portions only at the bristle free end so that the islands in a sea composite fibers with the core bristles formed in a specified length are implanted in a bristle base (see Patent Document 4), a toothbrush formed by implanting a brush formed into a shape with a plurality of unit cross-sectional elements which form a predetermined shape such as circle, ellipse, triangle, or hexagon linked for the base cross-sectional shape on a bristle base surface, immersing the brush in an acid or alkali, or other chemical solution, splitting the brush free end portion into a plurality, and forming each of split bristles in a sharp taper (see Patent Document 5), and a toothbrush having a plurality of sharp tapered split bristles formed at the free end portion and at the same time having a brush with other split bristles whose lengths are varied with respect to specific split bristles implanted (see Patent Document 6).
The toothbrushes as described above with tapered bristles of various shapes implanted in a bristle base have excellent suitability for bristle insertion into narrow portions, such as the gaps between neighboring teeth and gaps between the teeth and the gums because of the free end shape of the tapered bristles and is highly effective in removing dental plaque and cleaning the teeth of the relevant portions. However, toothbrushes using conventional tapered bristles as described above have tufts of synthetic resin filaments at least with one end formed in a taper form folded into two in a U-shape and fitted and fixed (driven) together with anchor (also called metal wire rod, wire staple, etc.) into tuft holes formed in a bristle base of a brush main body formed beforehand by injection-molding of synthetic resin. However, in the event that bristle tufts are driven into tuft holes of the bristle base using anchor, there is a restriction in the thickness of the bristle base which is unable to be reduced excessively, and there is a limitation in the density of the bristle tuft to be implanted into one tuft hole.
In the event that bristles processed to have tapered bristles beforehand are implanted into a bristle base, implantation using anchor as described above prevents the free end from being cut to an even length by trimming after implantation, and the bristled surface is held as implanted. However, in the case of implantation using anchor, the bristles are bent in a U-shape at the portion where bristles between the tuft hole bottom surface and anchor are inserted, but as a matter of course, a slight level difference is generated at the bent position, and this level difference causes the bristled surface to be irregular. That is, by the implantation using anchor, it is unable to manufacture a toothbrush which has an bristled surface with the free end aligned using bristles whose free ends are processed in advance. However, because the shape (configuration) of the bristled surface has big effects on cleaning the teeth and removing dental plaque, the shape of the bristled surface is extremely important in toothbrushes.
On the other hand, as a method for fixing bristles to the toothbrush bristle base, in addition to the above-mentioned method of using anchor, there proposed are many manufacturing methods of toothbrushes with bristles fixed to the bristle base without using anchor (anchorless toothbrushes), such as so-called in-mold process to fix bristles to a bristle base by forming a thick portion wider than the hole diameter of tuft holes or tuft diameter at the base portion of tufts, for example, a fused mass formed by fusion-bonding, disposing the thick portion in a molding cavity at the time of molding the brush main body, filling the cavity with molding material of the brush main body, and molding the brush main body (for example, see Patent Documents 7 to 9), and a method for preventing leakage of molding material at the time of molding a brush main body by mounting bristles to a bristled part cover (primary molded handle section) and then molding this bristled part cover integrally with the bristle base (secondary molded handle section) (see Patent Documents 10, 11, etc.), and a so-called fuse-in process in which a plurality of holes (tuft holes) are formed to house bristles (setae) into a bristle base (also called a bristle holder or bristled part), fixed-side base end portion of the bristles is heat-fused without molding the tuft holes, further the bristle length is shortened to form a thick portion (also called a thickened area and enlarged portion) at the fixed end section, and the base end portion of molten bristles is fusion-bonded to the bristle base (see Patent Documents 12, 13, etc.). Furthermore, there is proposed a toothbrush in which a head insert is bonded to a bristle base (head section) of a brush main body after fixing the base end portion (non-needlelike section) of a needlelike bristles by heat-fusing after the base end portion is pressed into a through-hole formed in a bristled part cover (head insert) of needlelike bristles whose free end is sharpened in a taper form (see Patent Document 14, etc.). According to these toothbrush manufacturing methods without using anchor, as compared to the method for driving bristle tufts together with anchor into tuft holes formed in the bristle base, the thickness of the bristle base can be reduced and ease of using the toothbrush in the oral cavity can be expected to be improved. In addition, the bristle implanting density of bristles can be increased as compared with the method using anchor. However, toothbrushes manufactured by the conventional anchorless toothbrush manufacturing methods had the bristled part formed by providing regular free end rounding processing by machining to the free end of bristles planted to the bristle base or mechanically dividing the free end after integrally fixing and planting bristles to the bristle base when the brush main body is molded by the above-mentioned manufacturing methods.
In addition, when bristles with the free ends processed in advance are fixed to the bristle base without using anchor, the free ends of bristles are unable to be mechanically or chemically processed after forming the bristle base to trim the shape of the bristle tuft free end portion or are unable to have the brush surface shapes composed with the free end of bristles. Therefore, the shape of the brush tuft free end and the brush surface shapes must be adjusted at the time of implanting. For example, in the insert process disclosed in Patent Documents 7 to 9, as shown in FIG. 15, a thick portion (fused mass) 31 is formed by fusing bristles 2 of the tuft 3 at the base end portion 30b of the tuft 3 formed by bundling bristles (setae) 2, and a cavity 140 is filled with molding resin material with the thick portion 31 disposed inside the cavity 140 of a brush molding dies 130 and the bristles 2 (tufts 3) are fixed to the bristle base of the brush main body, but when the thick portion 31 is formed at the base end portion of the tuft 3 and is disposed within the cavity 140, the free end 30a side tapered at each tuft 3 is brought in contact with a backplate 110, and the free end shape of the tuft 3 and the shape of the brush surface f composed with bristles 2 must be adjusted in advance. In addition, in the manufacturing method of a anchorless toothbrush by the fuse-in process disclosed in the Patent Document 12, for example, as shown in FIG. 19, the base end 30b side of the tuft (bristle tuft) 30 of bristles 2 is melted to form the thick portion (thickened portion, molten mass) 31, and this is fusion-bonded to the bristle base (bristle supporter) 12 of the brush main body 10 formed in advance. Furthermore, in the manufacturing method of anchorless toothbrushes by the fuse-in process disclosed in the Patent Document 13, as shown in FIG. 20, the base end portion 30b of the bristles tuft (bristles bundle) 30 is fused to form the thick portion (enlarged termination portion) 31 and at the same time, the bristled surface 12a of the bristle base (bristle base) 11 of the brush main body 10 is fused, and furthermore, tuft holes (dented holes) 6 are formed on the bristled surface 12a as shown in FIG. 21, and the fused thick portion 31 is heat-fused to the fused bristled surface 12a or tuft holes 6 formed on the bristled surface 12a to fix the tuft 3 to the bristle base 12. In these processes disclosed in Patent Documents 12 and 13, when the thick portions 31 is formed in the base end portion 30b of the tuft 3 and this is fused to the bristled surface 12a of the bristle base 12, the tapered bristle free end side (free end side) 30a of each tuft 3 is brought in contact with backplates 410 and 510 and the free-end shape of the tuft 3 and the shape of brush surface f composed with bristles must be adjusted in advance.
As described above, when the bristles with the free end processed in advance are implanted to the bristle base and the bristled part is formed without using anchor, post-processing after implantation is unable to be performed, and therefore, at the time of implantation, the free end portion of bristles with the free end processed is brought in contact with the backplate, etc. and under the aligned condition, operations must be performed. However, in the case of bristles formed simply into a tapered shape for increased cleaning efficiency, the free end is slender and is scarcely elastic, the tapered free end portion is brought into contact with the backplate at the time of implantation operation and the free end is aligned, the relevant free end portion is bent or broken, the free end of bristles after implantation tends to be not uniform, and it is difficult to adjust the brush surface composed with the free end portion of tufts and free end to a desired shape.    Patent document 1: Japanese Unexamined Patent Publication No. H6-141923    Patent document 2: Japanese Unexamined Patent Publication No. H7-284412    Patent document 3: Japanese Unexamined Patent Publication No. H11-75939    Patent document 4: Japanese Unexamined Patent Publication No. H9-322821    Patent document 5: Japanese Unexamined Patent Publication No. 2003-144229    Patent document 6: Japanese Unexamined Patent Publication No. 2003-199626    Patent document 7: Examined Patent Publication (Kokoku) No. H6-16725    Patent document 8: Patent Publication No. 2732875    Patent document 9: National Publication of Translated Version No. H9-512724    Patent document 10: Japanese Unexamined Patent Publication No. H9-182632    Patent document 11: Japanese Unexamined Patent Publication No. 2003-102552    Patent document 12: Japanese Unexamined Patent Publication No. H2-99002    Patent document 13: Examined Patent Publication (Kokoku) No. H6-46962    Patent document 14: Japanese Unexamined Patent Publication No. 2004-181215